Usability Validation of PFL-X: A Minimal Protocol for Testing Readability Interpretability and Independent Application

This document presents a minimal validation protocol for assessing the usability of the Pressure-Flow Language Extension (PFL-X) within the Paton System. While prior work establishes the structural and cross-domain validity of admissibility flow, this protocol evaluates whether the symbolic language can be understood, interpreted, and applied by individuals without prior instruction. The protocol tests whether PFL-X functions as a human-readable interface layer capable of transmitting structural understanding across users, domains, and contexts with minimal explanation. Participants are asked to interpret symbols, identify overload conditions (>>O<<), recognise collapse states (X), and apply the symbolic language to real-world situations. Two conditions are defined: no explanation and minimal explanation. The protocol measures readability, interpretability, applicability, and consistency across independent users. Pass conditions are achieved if users can correctly infer meaning and apply the symbolic structure without formal training. Failure occurs if interpretation requires detailed explanation or cannot be applied consistently. This work does not evaluate predictive accuracy or domain-specific performance. It evaluates usability only: whether the symbolic system can function as a transferable representation layer between individuals and domains. The protocol supports the claim that admissibility flow can be communicated and applied independently of formal theory, establishing PFL-X as a viable human-interface language for constraint-based systems.